Glen Canyon Dam’s evaporating hydropower

Ever since water levels in Lake Powell started dropping in 1999, the last time the reservoir was near full, I’d heard a lot about the infamous bathtub ring—the white band of minerals and salts that separates the current lake level from the high water mark. So I was looking forward to seeing it for myself when I headed out on a rafting trip down Cataract Canyon, below the confluence of the Green and Colorado rivers, two weeks ago. What stuck me most as I floated down the river was not the ring, but the inhospitality of those re-emerging shorelines. Oozing silty beaches that sucked you in up to your knees, eroding sandy cliffs and thickets of tumbleweeds were a staple of the lower third of the trip, where the river merged with the reservoir. At the takeout, what used to be a short, gravelley boat ramp has become a long slog up a sandy hill to a parking lot that was once on the shore. Perhaps the only upside of the lake’s recession was the widespread die-off of tamarisks stranded tens of feet above the new, lower waterline.

The government entities that manage Glen Canyon Dam and sell the power its turbines generate are also distressed at Lake Powell’s retreat, albeit for economic and political reasons. According to the Bureau of Reclamation, in May the reservoir was only 48 percent full, and is expected to drop 11 feet before September, ending the summer at 44 percent capacity. Severe to extreme drought in much of the Colorado River’s watershed, plus record heat, isn’t exactly helping.

Despite the dismal conditions, Glen Canyon Dam is still discharging 8.23 million acre-feet of water this year (measured from Oct. 1, 2012 to Sept. 30), as it does every year that lake levels stay above approximately 3,650 feet (the exact levels were decided in a 2007 environmental impact study designed to address water storage issues on the Colorado River in times of drought). But there’s a 50-50 chance that the lake will soon drop below that height, triggering a lower water release next year. If that happens, it would be the first time since Lake Powell’s creation that less than 8.23 million acre feet of water will pass from Glen Canyon Dam, according to Bureau of Reclamation spokesperson Lisa Iams. “It’s not a promising statement about the hydrology that all of us face,” she said. “The realities of drought and climate change are increasing.”

Drought is bad for electricity generation at Glen Canyon Dam for two primary reasons: One, when lake levels are low enough to merit a smaller release (like they could be this coming year), less water goes through the turbines, producing less energy. That hasn’t happened yet, but the dam has already seen a reduction in electricity generation. Here’s why: Lower water levels mean there is less pressure on the water as it passes through the turbines. “As our lake level drops, the same volume of water going through the dam generates less electricity,” explained Jason Tucker, facility manager for Glen Canyon Dam. “The deeper the water, the more energy there is for making electrical power.”

As lake levels have dropped (solid line), so has the amount of power being generated (dotted line). Courtesy Argonne National Laboratory.

As a result of the reduction in power generation, Western Area Power Administration, the government body that sells Glen Canyon’s electricity, has told its buyers to expect less electricity from the dam, according to spokesman RandyWilkerson.

Elsewhere in the West, drought has actually raised the price of hydropower. Decreased electricity generation from Missouri River dams has forced WAPA to buy power on the open market to fulfill its obligation to customers in eastern Montana, the Dakotas and eastern Colorado (WAPA’s contracts with buyers of Glen Canyon’s electricity don’t require the agency to do this). Customers in the Missouri River basin now see something called a “drought adder” on their electricity bills, which shows what percentage of the rate hike is due to drought.

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It is inaccurate to say the dam supplies enough energy for 5.8 million people. Five billion kwh is "enough" energy for around a million people. The Bureau's weblink puffs up their own contribution to the grid, because 5.8 million people receive some energy from Glen Canyon, but not all of their energy.

Ricardo Small

Jul 09, 2013 02:02 PM

Glenn Canyon Dam was a bad idea from the giddy-up. It destroyed Glenn Canyon, which was another Grand Canyon. It flooded uncounted 1st nation ruins. It made Katie Lee cry. Read her book: All My Rivers Are Gone - A Journey of Discovery Through Glen Canyon. Glenn Canyon Dam should be renamed Dominy's Dike, so the blame for enabling such a boondoggle rests where it belongs. Floyd Dominy was the Bureau of Reclamation's honcho who destroyed so many of the West's wild water resources.

chuck dunn

Jul 09, 2013 06:03 PM

DAMS SERVE A GOOD PURPOSE..CLEAN ENERGY VS COAL FIRED POWER PLANTS.. OUR GREAT GOVERNMENT IS REMOVING DAMS ON THE KLAMATH RIVER IN NORTHERN CALIFORNIA,THE DEMAND FOR ENERGY WILL ONLY GO UP SO BY REMOVING THESE DAMS TO SUIT THE CRAZY ENVIRONMENTALISTS WE WILL CREAT MORE POLLUTION.. LESS CONTROL OF THE WATER IN TIMES OF FLOODS AND NOT HAVE A RESERVE FOR DROUGHT YEARS.P AM OPPOSED TO FRACKING IN WATER SENSITIVE AREAS.THE ADDED CHEMICALS AND THE LARGE AMOUNT OF WATER USED MAKE FOR A GREAT DANGER.

chuck dunn

Jul 09, 2013 06:13 PM

DAMS SERVE A GOOD PURPOSE..CLEAN ENERGY VS COAL FIRED POWER PLANTS.. OUR GREAT GOVERNMENT IS REMOVING DAMS ON THE KLAMATH RIVER IN NORTHERN CALIFORNIA,THE DEMAND FOR ENERGY WILL ONLY GO UP SO BY REMOVING THESE DAMS TO SUIT THE CRAZY ENVIRONMENTALISTS WE WILL CREAT MORE POLLUTION.. LESS CONTROL OF THE WATER IN TIMES OF FLOODS AND NOT HAVE A RESERVE FOR DROUGHT YEARS.P AM OPPOSED TO FRACKING IN WATER SENSITIVE AREAS.THE ADDED CHEMICALS AND THE LARGE AMOUNT OF WATER USED MAKE FOR A GREAT DANGER.

Wes Hopper

Jul 09, 2013 06:51 PM

It's going to be fun here in AZ when the CAP goes dry. I believe it will happen in my lifetime, and I'm already an old-timer.

Wanda Ballentine

Jul 09, 2013 10:58 PM

It appears that we have now learned that dams can create CO2!!!

http://www.globalpost.com/d[…]ms-emissions-climate-changeBrazil's hydro dams could make its greenhouse gas emissions soarAlready a top emitter, Brazil could spew hundreds of millions more tons of gases blamed for climate change, such as CO2 and methane, as it floods Amazon forest for hydro power, researchers say.